Developing device of the wet developing agent type for electrophotographic duplication

ABSTRACT

A device wherein a coat of a developing agent adhesion preventing material is applied to the surface of an opposed electrode plate disposed in juxtaposed relation to a photosensitive body. A viscous developing liquid of high toner concentration is supplied to a space between the photo-sensitive body and the developing agent adhesion preventing material layer of this opposite electrode plate by a liquid circulating mechanism so as to convert an electrostatic latent image on the photosensitive body into a toner image capable of being transferred to copy sheets.

Moehizuki tee atent [1 1 Sept. 11, 1973 DEVELOPING DEVICE OF THE WET DEVELOPING AGENT TYPE FOR ELECTROPHOTOGRAPHIC DUPLICATION [75] Inventor: Nobuo Mochizuki, Matsudo,

Chiba-ken, Japan [73] Assignee: Ricoh Co., Ltd., Tokyo, Japan [22] Filed: Nov. 28, 1972 [21] Appl. N0.: 310,154

[30] Foreign Application Priority Data Dec. 7, 1971 Japan 46/99226 [52] US. Cl 355/10, 95/89 R, 118/D1G. 23 [51] int. Cl G03g 15/10 [58} 'Field of Search 355/3, 10, 15;

95/89 R, 94 R; 118/637, DIG. 23, DIG. 24

[56] References Cited UNITED STATES PATENTS 2,253,060 8/1941 Clearman 95/94 R X 3,284,224 11/1966 Lehmann 355/10 X 3,334,613 8/1967 Young 118/637 3,682,542 8/1972 MacKenzie 355/10 Primary Examiner-Fred L. Braun Attorney-Henry T. Burke et a1.

[57] ABSTRACT A device wherein a coat of a developing agent adhesion preventing material is applied to the surface of an opposed electrode plate disposed in juxtaposed relation to a photosensitive body. A viscous developing liquid of high toner concentration is supplied to a space between the photo-sensitive body and the developing agent adhesion preventing material layer of this opposite electrode plate by a liquid circulating mechanism so as to convert an electrostatic latent image on the photosensitive body into a toner image capable of being transferred to copy sheets.

I 6 Claims, 2 Drawing Figures DEVELOPING DEVICE OF THE WET DEVELOPING AGENT TYPE FOR ELECTROPIIOTOGRAPI'IIC DUPLICATION BACKGROUND OF THE INVENTION This invention relates to a developing device of the wet developing agent type for electrophotographic duplication.

In developing an electrostatic latent image in ordinary electrophotographic duplication, a developing liquid used comprises a pigment and a resin which are generally in a ratio 1:1 to 1:10. Developing liquids of this range of component ratios are low in transfer duplication efficiency. It has thus been usual practice to increase the component ratio of developing liquids to 1:5 to 1:300 so as to increase toner concentration and to use as the resin component a material showing high viscosity when transfer duplication is carried out whereby transfer duplication efficiency can be increased.

The use of such viscous developing liquids of high toner concentration for developing an electrostatic latent image has a disadvantage in that the stream of the liquid stagnates and the materials contained in the liquid tend to be deposited in the path of movement of the liquid so as to block the passage of liquid unless means are provided for promoting the flow of the stream of the developing liquid through its circulation passage.

Particularly in cases where developing of an electrostatic latent image is carried out by causing a developing liquid to flow between a photosensitive body and an opposite electrode plate disposed in juxtaposed relation thereto, it is advantageous to minimize the space between the photosensitive body and the opposite electrode plate and to electrically insulate the opposite electrode plate from outside, because in this way adhesion of the toner to the latent image can be accomplished satisfactorily. This, however, has the disadvantage of solid components (hereinafter referred to as a developing agent) of the developing liquid adhering to the surface of the opposite electrode plate and being accumulated in the course of use.

SUMMARY OF THE INVENTION This invention has as its object the provision of a developing device of the wet developing agent type for electrophotographic duplication which permits a viscous developing liquid of high toner concentration to flow smoothly in a stream on the opposite electrode plate without stagnating in the passage for-liquid flow defined by such plate.

In the subject matter to which the present application is directed, in developing apparatus of the general type described above including an opposite electrode plate juxtaposed to a photosensitive surface, the invention contemplates the provision of a coat of a developing agent adhesion preventing-material, such for example as a silicone resin, tetrafluoroethylene or the like, on the surface of the opposite electrode plate on which a stream of a developing liquid of high toner concentration is forcedly supplied by liquid circulating means, such for example as a pump. The presence of such coat is effective to prevent stagnation of the stream of the developing liquid on the opposite electrode plate and adhesion of the developing agent to the surface of the opposite electrode plate, no matter how viscous the liquid is and no matter how high its toner concentration 3a may have a thickness in a range from 1: to .100 uthe Further features and advantages of the invention will be apparent from the detailed description hereinbelow set forth, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a developing device of the wet developing agent type for electrophotographic duplication comprising one embodiment of this invention; and

FIG. 2 is a perspective view of the opposite plate section of the device shown in FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT In FIG. 1, a drum 2 supported by a shaft 1 is directly provided on its peripheral surface with a layer of a photosensitive material, such for example as selenium, cadmium sulfide, poly-N-vinyl carbazole or the like. The drum 2 is adapted to be rotated in the direction of an arrow a and subjected to electric charging and exposing to an optical image of an original by known means (not shown). The photosensitive material layer may be indirectly provided on the peripheral surface of the drum 2 as by applying to the drum a sheet-material on which the photosensitive layer is formed. Recording paper on which an electrostatic latent image is formed may be used in place of the sheet material.

A developing tray 4 supporting on its surface an op.- posite electrode plate 3 made of metal isdisposed downwardly rightwardly of the drum 2, the opposite electrode plate 3 being disposed along substantially one fourth the extent of the lower half of the peripheral surface of the drum 2 and adapted to face the photosensitive material layer on the peripheral surface of the drum with a very small clearance between them. As the drum 2 rotates, the photosensitive material layer on the peripheral surface of the drum formed thereon with the electrostatic latent image of the original by being subjected to electric charging and exposing to an optical image of the original is brought to a position in which it is juxtaposed to the surface of the opposite electrode plate 3 on which a developing liquid is supplied.

A developing agent adhesionv preventing material coat 3a of a very small thickness is formed on the surface of the opposite electrode plate 3 which faces the photosensitive material layer on the drum 2. The coat thickness of the coat 3a being determined such that the function of the opposite electrode plate 3 is not interfered with.

The developing agent adhesion preventing material may be selected from the group consisting of a silicone resin, tetrafluoroethylene, polyurethane, polypropylene,'polyethylene, polyester, nylon, vinylidene chloride, vinyl chloride, polycarbonate and cellulose acetate. One of these materials is applied as a coat to the surface of the opposite electrode plate 3 by known means. A voltage of a polarity commensurate with the polarity of the charge carried by the photosensitive material layer on, the drum is impressed on the opposite electrode plate 3. Alternatively, the opposite electrode plate 3 may be grounded or electrically cut off.

A drain 5 is provided in a left .end of the bottom of the developing tray 4 as ,seen in FIG. 1, and a funnelshaped receiver 6 having a sharply inclined 'conical wall opens below the lower end of the drain 5, the receiver 6 being connected at its narrowed lower end to a bent pipe 7 connected to a pump 8 for moving a developing liquid in a circulating stream. The conical wall of the receiver 6 is inclined at an angle no smaller than 30 C.

A developing liquid 9 (e.g. a viscous liquid of high toner concentration) in the receiver 6 is supplied under high pressure by the pump 8 through a pipe 10 to a nozzle 11 shown in FIG. 2 which is formed by pressing the front end of the pipe 10 into planar form.

The nozzle 11 includes a planar orifice 11a which opens above a space A between the peripheral surface of the drum 2 on which the photosensitive material layer is formed and the coated surface 3a of the opposite electrode plate 3 as shown in FIG. 1.,The developing liquid 9 is caused to flow under high pressure into the space A by the action of the pump 8.

The stream of the developing liquid flows down in the space A as indicated by an arrow. The provision of the layer 3a is effective to prevent adhesion of the developing agent to the opposite electrode plate 3 and enables to convert an electrostatic latent image on the peripheral surface of the drum 2 into a toner image satisfactorily. The stream of the developing liquid can thus be moved smoothly in circulation into the receiver 6 through the developing tray 4.

It is to be understood that theinvention is not limited to the features and embodiments hereinabove specifically set forth but may be carried out in other ways without departure from its spirit.

I claim:

1. A developing device of the wet developing agent type for electrophotographic duplication using a viscous developing liquid of high toner concentration, comprising:

a. means, including a photosensitive body, for forming an electrostatic latent image on the photosensitive body;

b. an opposite electrode plate disposed in close proximity to said photosensitive body in face-to-face relation thereto for developing the electrostatic latent image, said photosensitive body and said plate defining a space between them for flow of developing liquid;

c. developing liquid supply means for supplying the developing liquid into said space between said photosensitive body and said opposite electrode plate to develop said electrostatic latent image by the developing liquid;

d. a pump adapted to cause a stream of the developing liquid to flow in circulation; and

e. a coat of a developing agent adhesion preventing material applied to the surface of said opposite electrode plate facing the photosensitive body.

2. A developing device as set forth in claim 1 wherein said photosensitive body is a drum formed on its peripheral surface with a photosensitive material layer, and said opposite electrode plate is disposed along the peripheral surface of the drum.

3. A device as set forth in claim 1 wherein said developing liquid supply means is a nozzle having a flat orifice at its forward end.

4. A developing device as set forth in claim 1 wherein I said developing agent adhesion preventing material is selected from the group consisting of a silicone resin, tetrafluoroethylene, polyurethane, polypropylene, polyethylene, polyester, nylon, vinylidene chloride, vinyl chloride,polycarbo nate and cellulose acetate.

5. A developing device asset forth in claim 1 wherein said coat of said developing agent adhesion preventing material has a thickness in a range from 1 to 100 p.

6. Apparatus for developing an electrotatic latent image, comprising: A V

a. means, including a photosensitive surface moveable along a defined path, for forming an electrostatic latent image on the photosensitive surface;

b. an electrode plate for cooperating with said photosensitive surface to develop the latent image by application of a developing agent, 'said plate having an extended surface disposed in facing, closely spaced relation to the path of movement of'said 1 photosensitive surface for defining therewith a space for developing liquid;

0. nozzle means for directing a flow of developing liquid containing a developing agent across said extended surface; and v d. a thin fixed layer of a developing agent adhesion preventing material, coating said extended surface. =0: :0: I 

2. A developing device as set forth in claim 1 wherein said photosensitive body is a drum formed on its peripheral surface with a photosensitive material layer, and said opposite electrode plate is disposed along the peripheral surface of the drum.
 3. A device as set forth in claim 1 wherein said developing liquid supply means is a nozzle having a flat orifice at its forward end.
 4. A developing device as set forth in claim 1 wherein said developing agent adhesion preventing material is selected from the group consisting of a silicone resin, tetrafluoroethylene, polyurethane, polypropylene, polyethylene, polyester, nylon, vinylidene chloride, vinyl chloride, polycarbonate and cellulose acetate.
 5. A developing device as set forth in claim 1 wherein said coat of said developing agent adhesion preventing material has a thickness in a range from 1 to 100 Mu .
 6. Apparatus for developing an electrotatic latent image, comprising: a. means, including a photosensitive surface moveable along a defined path, for forming an electrostatic latent image on the photosensitive surface; b. an electrode plate for cooperating with said photosensitive surface to develop the latent image by application of a developing agent, said plate having an extended surface disposed in facing, closely spaced relation to the path of movement of said photosensitive surface for defining therewith a space for developing liquid; c. nozzle means for directing a flow of developing liquid containing a developing agent across said extended surface; and d. a thin fixed layer of a developing agent adhesion preventing material, coating said extended surface. 